1. Field of the Invention
The invention relates to a connecting element for measuring an actuating force of a vehicle brake system.
2. Description of the Prior Art
Hydraulic vehicle brake systems have a connecting element which is typically called a pedal rod or piston rod, and which connects a user control element of the vehicle brake system with an input element of the vehicle brake system. The user control element is the element or component at which an actuating force is introduced into the vehicle brake system. In conventional vehicle brake systems, it is a (foot) brake pedal or, especially in motor cycles, a (hand) brake lever. The input element of conventional hydraulic vehicle brake systems is the so-called primary piston or rod piston of the master cylinder, which is connected to the brake pedal or brake lever by the connecting element, namely the pedal rod or piston rod. The connecting element transmits the actuating force, that is, the muscle power exerted on the brake pedal or the brake lever, to the input element, or in other words to the primary piston or rod piston of the master cylinder. However, the invention is not limited to the so-called pedal rod or piston rod as a connecting element; instead, it is directed in general to a connecting element which transmits the actuating force.
In many publications, measuring the actuating force of a vehicle brake system is claimed; typically, this involves a force sensor or the like, without explaining the structure and mode of operation thereof. For instance, published German patent application DE 103 27 553 A1, whose subject is an electromechanical brake booster, discloses a force sensor that is disposed in a piston rod.
Published German patent application DE 199 36 433 A1 is comparable, whose subject is an electromagnetic brake booster and which has a force-tension converter that is disposed between a pedal and a piston rod, the piston rod being disposed in the extension of the pedal rod.
The subject of published German patent application DE 103 18 850 A1 is a vehicle brake system with hydraulic brake boosting. It has a master cylinder, whose primary piston or rod piston, on its back side toward a brake pedal, can be hydraulically subjected to pressure from an external energy source. The master cylinder has a pedal travel simulator, which includes a simulator spring. The pedal travel simulator, in a way that is as close to reality as possible, simulates a pedal force/travel characteristic of the kind that conventional hydraulic vehicle brake systems with or without brake boosting have, so that a driver has the pedal feel he is used to. The master cylinder of the known vehicle brake system accordingly does not have a rigid piston rod but rather a pedal rod or piston rod that shortens spring-elastically upon subjection to force, because of the simulator spring. Measuring the actuating force is not disclosed; instead, what is measured is a travel of the pedal rod or piston rod, or in the final analysis a pedal travel.
Published German patent application DE 100 57 557 A1 discloses an electromechanical brake booster, in which a force sensor is disposed between a pedal rod and a piston rod disposed in the extension of the pedal rod. A reaction disk is also disposed between the pedal rod and the piston rod, for the sake of comfortable actuation. As a result of its disposition, the reaction disk is disposed in series with the force sensor.